Results of radiocarbon and optical dating confirm that occupation debris in Australia's Jinmium Rockshelter is no more than 10,000 years old, according to geochronologist Richard Roberts of La Trobe University in Melbourne. The site made headlines in late 1996 when its discoverers claimed that the earliest occupation levels were between 116,000 and 176,000 years old, an age that would have required a major rethinking of Australia's colonization (see "Ancient Seafarers," March/April 1997).

Fearing that the original samples taken from the site had been contaminated by grains of sediment that were not "fully bleached" by sunlight before burial (and thus whose luminescence clocks had never been set to zero), Roberts and a team of researchers took fresh samples from the site, dating each grain by grain. "There now seems to be little doubt that the original claims were far too old," says Roberts. "The advent of single-grain methods should ensure such dating mishaps soon become another artifact of the past."